1. Field of the Invention
This invention relates to controllable-attenuation devices such as may be used to control the volume level of an audio signal. More particularly, this invention relates to variable-attenuation apparatus utilizing a digital-to-analog converter.
2. Description of the Prior Art
Variable attenuation devices have been used for many years in numerous applications. One common application is in the field of sound reproduction where it is desired to adjust the sound level to provide for preferred listening conditions. Such an adjustment can easily be effected by the use of a conventional potentiometer, as in the usual volume control. More recently, however, it has been desired to make such adjustments from a remote location, as by means of an electrical signal, and this result cannot be achieved economically by conventional volume-control apparatus.
It has been suggested that a digital-to-analog converter may be employed to adjust the level of an audio signal. Such a proposal is set forth in the article "Get Wide-Range Digitally Controlled Attenuation with a Companding D/A" by Walter Jung and Will Ritmanich, appearing in Electronic Design 23, for Nov. 8, 1978. That proposal however suffers from important disadvantages, particularly in requiring a relatively complex and therefore costly circuit arrangement.